Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the ... [more ▼]

Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the C2 parent species C2H2 and C2H6. We combine these observations to investigate the origin of cometary C2. The observed C2 column densities are inconsistent with a production of C2 from C2H2, C2H6, and C3. Based on a photochemical model, we quantitatively discuss the influence of further potential C2 parent species. The assumption of C4H2 as an additional C2 parent species in comet 8P/Tuttle provides the best explanation for the observed C2 column densities. [less ▲]

We report on simultaneous optical and infrared spectroscopic observations of the Jupiter Family comet 103P/Hartley2 performed with the UT-1 and UT-2 8-m Unit Telescopes of the ESO Very Large Telescope ... [more ▼]

We report on simultaneous optical and infrared spectroscopic observations of the Jupiter Family comet 103P/Hartley2 performed with the UT-1 and UT-2 8-m Unit Telescopes of the ESO Very Large Telescope (VLT). These coordinated observations were carried on during several nights (2010 Nov. 5, 9, 10 and 11 UT) around the NASA EPOXI encounter with the comet on Nov. 4 [1] and in support to the key program « Water and related chemistry in the Solar System » (HssO) [2] of the Herschel Space Observatory. From high resolution optical spectroscopy of the CN (0,0) 388 nm band using UVES at UT2 we determined the isotopic ratios 12C/13C = 95 ± 15 and 14N/15N = 155 ± 25 in the CN radical. From the NH2 (0,9,0) and the H2O+ bands around 600 nm, we derived a nuclear spin temperature of 33 ± 3 K for NH3 and 36 +7/-6 K for H2O. These values are similar to those found in Oort- Cloud and Jupiter Family comets. From lowresolution long-slit spectroscopy with FORS2 at UT1 we will determine the CN, C2 and C3 spatial profiles and their production rates. From the high-resolution near-IR spectra that we collected with CRIRES at UT1 we will measure simultaneously the production rates and mixing ratios of the parent molecules H2O, HCN, C2H6, and CH3OH that are well detected in our spectra and we will study the link to the daughter species. [less ▲]

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very ... [more ▼]

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very Large Telescope) with the CRIRES instrument as part of a multi-wavelength observation campaign of 8P/Tuttle performed in late January and early February 2008. Radar observations suggested that 8P/Tuttle is a contact binary, and it was proposed that these components might be heterogeneous in chemistry. We determined mixing ratios of organic volatiles with respect to H[SUB]2[/SUB]O and found that mixing ratios were consistent with previous near infrared spectroscopic observations obtained in late December 2007 and in late January 2008. It has been suggested that because 8P/Tuttle is a contact binary, it might be chemically heterogeneous. However, we find no evidence for chemical heterogeneity within the nucleus of 8P/Tuttle. We also compared the mixing ratios of organic molecules in 8P/Tuttle with those of both other HFCs and long period comets (LPCs) and found that HCN, C[SUB]2[/SUB]H[SUB]2[/SUB], and C[SUB]2[/SUB]H[SUB]6[/SUB] are depleted whereas CH[SUB]4[/SUB] and CH[SUB]3[/SUB]OH have normal abundances. This may indicate that 8P/Tuttle was formed in a different region of the early solar nebula than other HFCs and LPCs. We estimated the conversion efficiency from C[SUB]2[/SUB]H[SUB]2[/SUB] to C[SUB]2[/SUB]H[SUB]6[/SUB] by hydrogen addition reactions on cold grains by employing the C[SUB]2[/SUB]H[SUB]6[/SUB]/(C[SUB]2[/SUB]H[SUB]6[/SUB]+C[SUB]2[/SUB]H[SUB]2[/SUB]) ratio. The C[SUB]2[/SUB]H[SUB]6[/SUB]/(C[SUB]2[/SUB]H[SUB]6[/SUB]+C[SUB]2[/SUB]H[SUB]2[/SUB]) ratio in 8P/Tuttle is consistent with the ratios found in other HFCs and LPCs within the error bars. We also discuss the source of C[SUB]2[/SUB] and CN based on our observations and conclude that the abundances of C[SUB]2[/SUB]H[SUB]2[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB] are insufficient to explain the C[SUB]2[/SUB] abundances in comet 8P/Tuttle and that the abundance of HCN is insufficient to explain the CN abundances in the comet, so at least one additional parent is needed for each species, as pointed out in previous study. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Prog. 080.C-0615 and 280.C-5053).We regret to note the death of Dr. J. -M. Zucconi in 2009 May. [less ▲]

We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good ... [more ▼]

We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space missions. From high resolution optical spectroscopy of the CN (0,0) 388 nm and NH[SUB]2[/SUB] (0,9,0) 610 nm bands using UVES at UT2 we determined [SUP]12[/SUP]C/[SUP]13[/SUP]C = 90 ± 10 and [SUP]14[/SUP]N/[SUP]15[/SUP]N = 150 ± 20 in CN and we derived a nuclear spin temperature of NH[SUB]3[/SUB] of 29 ± 1 K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit spectroscopy with FORS1 at UT2 we determined the CN, C[SUB]3[/SUB] and C[SUB]2[/SUB] production rates and the parent and daughter scale lengths up to 5.2 10[SUP]5[/SUP] km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and mixing ratios of H[SUB]2[/SUB]O, HCN, C[SUB]2[/SUB]H[SUB]2[/SUB], CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH. [less ▲]

in Käufl, H. U.; Sterken, C. (Eds.) Deep Impact as a World Observatory Event: Synergies in Space, Time, and Wavelength (2009)

The Deep Impact target comet 9P/Tempel 1 was observed by means of long-slit spectroscopy from two nights before impact up to eight nights after impact, using the ESO VLT UT1, UT2, and ESO NTT telescopes ... [more ▼]

The Deep Impact target comet 9P/Tempel 1 was observed by means of long-slit spectroscopy from two nights before impact up to eight nights after impact, using the ESO VLT UT1, UT2, and ESO NTT telescopes. Spectra covering the complete optical wavelength range were obtained, and information at different position angles in the coma was collected. The data were used to study the gas and dust activity of comet 9P/Tempel 1. Gas production rates before and after impact and the amount of material in the impact cloud were determined. The pre-impact Afρ parameter, the dust production rate and the dust-to-gas mass ratio were derived. A variation of the cometary gas activity with rotation of the nucleus was detected. A difference in the variation of the brightness of the CN gas emission band compared to the variation of the emissions by C_2, C_3, and NH_2 in the inner coma suggests compositional differences between different parts of the surface of comet 9P/Tempel 1's nucleus. [less ▲]

in Käufl, H. U.; Sterken, C. (Eds.) Deep Impact as a World Observatory Event: Synergies in Space, Time, and Wavelength (2009)

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its ... [more ▼]

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its position and shape are governed by the physical properties of the dust grains. We use a Monte Carlo model to describe the evolution of the post-impact dust plume. The results of our dynamical simulations are compared to the data obtained with FORS2footnote{FORS stands for \underline{FO}cal Reducer and low dispersion Spectrograph for the Very Large Telescope (VLT) of the European Southern Observatory (ESO).} to derive the particle size distribution and the total amount of material contained in the dust ejecta cloud. [less ▲]

in Käufk, H. U.; Sterken, C. (Eds.) Deep Impact as a World Observatory Event: Synergies in Space, Time, and Wavelength (2009)

Around the time of the impact of NASA's Deep Impact (DI) mission at comet 9P/Tempel 1, in total 6 telescopes with altogether 7 different instruments, located at the La Silla (LSO) and Paranal (VLT ... [more ▼]

Around the time of the impact of NASA's Deep Impact (DI) mission at comet 9P/Tempel 1, in total 6 telescopes with altogether 7 different instruments, located at the La Silla (LSO) and Paranal (VLT) Observatories of the European Southern Observatory (ESO) in Chile, were used to characterize the dust properties before and after the event. The ejecta cloud expanded at an average speed of about 200 ms[SUP]-1[/SUP]during the first hours after the event. It reached stagnation distance of 25000 km about 3 days after impact. The pre-impact dust jet and fan activity (`porcupine' pattern) remained undisturbed after impact. In our measurements the jet activity can be traced to a few 100 km nucleus distance. In total 9 comastructures are identified which may originate from at least 4 regions of enhanced dust emission on the nucleus - one of this region may in fact be multiple. No obvious signatures of a new active region created by DI are found. The overall dust production during the impact compares to about 5-10 h of normal activity. The global expansion geometry of the DI cloud is compatible with a majority of dust grains in the micron size range. Indications exist for asymmetric brightness and colour distributions of the dust in the ejecta cloud. The dust temperature rose from about 280-290 K before to 330 K one day after the event and fell to pre-impact level the day thereafter. The dust reflected sunlight was found to be linearly polarized at about 7.5% in the visible and near-IR, at constant level within about 4000 km from the nucleus. No circular polarization of the dust is detected. [less ▲]

in Bulletin of the American Astronomical Society (2008, September 01), 40

We present near-infrared observations of organic molecules in comet 8P/Tuttle. Comet 8P/Tuttle is a Halley-type comet and its last perihelion was in early January 2008. Our observations were carried out ... [more ▼]

We present near-infrared observations of organic molecules in comet 8P/Tuttle. Comet 8P/Tuttle is a Halley-type comet and its last perihelion was in early January 2008. Our observations were carried out on January 28 and February 4 using CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) at the Very Large Telescope (VLT). We used a 0.2" slit which provided a spectral resolving power of 80,000. We detected H[SUB]2[/SUB]O, OH, HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] on Jan 28, and H[SUB]2[/SUB]O, OH, CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH on Feb 4. We find that 8P/Tuttle is depleted in HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB] relative to H[SUB]2[/SUB]O compared with most other Oort cloud comets studied to date. Perhaps these depletions suggest that 8P/Tuttle formed in a different region from most Oort cloud comets, but it is also possible that the depletions are caused by repeated passages through the inner solar system. [less ▲]

Aims.We present observations of CN emission and the scattered solar light on cometary dust particles around the impact time of the Deep Space spacecraft (NASA) into the nucleus of comet 9P/Tempel 1. The ... [more ▼]

Aims.We present observations of CN emission and the scattered solar light on cometary dust particles around the impact time of the Deep Space spacecraft (NASA) into the nucleus of comet 9P/Tempel 1. The purpose of the observations was to compare post-impact activity to the conditions pre-impact to search for new spectral emission lines after impact, to quantify the increase in gas activity due to the impact and to study the long-term activity changes.<BR /> Methods: .We performed long-slit spectroscopy observations of comet 9P/Tempel 1 at the VLT, ESO, using the FORS instruments from July 2 to July 12, 2005. A wavelengths range of 370-920 nm was covered using two grisms. Four different position angle settings of the slit were applied each night with the projected Sun-comet line as standard setting, for which we report results here.<BR /> Results: .The optical spectra of comet 9P/Tempel 1 showed the usual emission bands in the optical wavelengths range of the radicals: CN, C3, C2 and NH2. No new emission bands were detected after impact. The ejecta cloud of gas and dust caused by the impacting spacecraft into the cometary nucleus could be followed over the observing period. The projected expansion velocities have been determined. The night after impact we observed about (3.9 ± 1.2) × 10[SUP]29[/SUP] molecules of the CN parent in the ejected cloud. However, after five days the appearance of the gas and dust coma was back to pre-impact conditions. <BR /> [less ▲]

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign ... [more ▼]

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics. [less ▲]

Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginning of May, 2004 at its closest approach to Earth. The observations consisted of quasi-simultaneous multi ... [more ▼]

Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginning of May, 2004 at its closest approach to Earth. The observations consisted of quasi-simultaneous multi-wavelength exposures in the visible, near-IR and thermal-IR in order to study different properties of the solid component that are responsible for the scattering and emission of radiation in different spectral ranges. The comet was observed with the 3.6m telescope, equipped with TIMMI2 for the thermal-IR region, the NTT, equipped with EMMI and SOFI for the visible and near-IR regions. Narrow band images and long slit spectra were recorded for each spectral region. In the near-IR range, polarimetric observations were also performed during the last night. The aim of the observations was the characterization of the solid component at small scalelength to search for possible short lifetime organic components, as those found in the comet C/2000 WM1 (Tozzi et al., 2004, A&A, 424, 235), dust fragmentation etc.. Here we report preliminary results of the analysis of these observations. [less ▲]